The primary objective of this proposal is to study how the thalamo- cortical pathways can be modified by sensory deprivation. Such an analysis will involve two phases. In the first we will examine - using conventional cell staining and measuring methods - the effects of lid suture upon the growth of cells in the lateral geniculate nucleus of the tree shrew. Once these changes have been established we will determine how they are related to modifications of the normal organization of the geniculostriate axon terminations that are produced by visual deprivation. This will involve placing small, restricted lesions within individual geniculate laminae of lid sutured tree shrews. The pattern of cortical degeneration will then be analyzed using various anterograde degeneration methods and compared with the known normal organization of geniculostriate terminations.